Die press safety system



Jan. 28, 1936. c. EKSERGIAN DIE PRESS SAFETY SYSTEM Filed July 22, 1930I N VEN TOR.

CARoLus L EKSERGAN A TTORNE Y.

. Patenteoi ian. 28,,1936

ED s'rArrss PATENT OFFICE;

2,028,768 .mr: mass SAFETY SYSTEM Carolus L. Eksergian, Detroit, Mich.,assignor to Edward Budd Manufacturing Company, Philadelphia, Pa., acorporation of Pennsylvania Application July 22, 1930, Serial No.469,784

7 Claims.

erating presses hand started, and particularly those in connection withwhich there are em-' ployed a number of operatives, the pressis'sometimes startedby oneof the operators before an.-

other has completed the attention he is giving the work on the machine.But while it is the special aim of this invention to relieve theseconditions and assure safety to the operatives of such presses, myinvention has a" wider scope still in its possible applicability to anymachines having working cycles and parts which analogously endanger thelimbs of their operatives.

Numerous systems and methods have heretofore been proposed to remedythese conditions. None of them, so far as I am aware, have beencompletely effective. Some-have been mechanical and some electrical. Themost common in intermittently operating presses has been the location ofthe control lever or, control button of the electrical control circuitat a distance so remote from the dies as to require the operator toremove his hands or himself from each of the dies in order to reach thecontrol.

Another device has been that of duplex control in which two controlelements have been provided, one for operation by. each hand of anoperative, whereby neither hand is available during control of the pressfor engagement with the machine or the work.

Yet with these and other safeguards, accidents have continued due, amongothers, to situations like the following. Power control devices or thepresses-at times stopped in the on position, thereby continuingoperation of the press expected by the operative to terminate at the endof the stroke. Operatives, sometimes-carelessly and sometimes in anendeavor to save time, oper-' ated dual control devices, both by onehand, and at the other, times blocked off one of the controls to avoidthe necessity of using both. The two operatives, once the press wasstarted, if the control system was such as to permit it to continue,'removedtheir hands from the control devices and gave attention to workon the machine before the completion of the down stroke, while there wasstill danger that the hands projected between the dies or other parts ofthe machine the same might result in As a general rule, control onceinstituted has been automatic for the completion of at least one fullstroke of the machine, and with control handles or push buttons, as thecase may be, the same might readily be released after initial actuation.Thisoperation has been favored because it permitted, more leisurely,picking up and presenting of the work for the succeedingoperation. Theobjects of my invention have especially to do with the meeting of thesesituations. More general objects of my invention are the attainment of aperfect safety system in which not 'only the special situation is met,but each and every other situation of danger to the operative iseliminated, the efficient combination of manual control by the operativeand automatic control 15 by the press, and the achievement of anefficient, simple and inexpensive safety system for large power pressesembodying servomotor control of the power cut on and cut oif devices.

The single figure of'the drawing is a diagram- 20 matic showing of thesystem, some parts being represented schematically, and others inelevation consequently the dimensions of the various parts in thedrawing are disproportionate to their true dimensions. 1

In this showing the press and the dies are subordinated to theenlargement and clarification of the general diagram of the system.For--the most part, the press is indicated in dotted lines. I0 is itsbed located on foundation II, l2 and I3 30 are the lower and upper dies,respectively, I4 the connecting rods, I5 the crank shaft, and IS theaxis of the crank shaft. A power cut on andcut off device isdiagrammatically represented by the showing of the pivoted lever I! ofthe form usually employed toactuate the'power cut on and cut off device.The'lever is usually pivoted to the frame of the press or its foundationI I and provided at its upper end with pull handle I8, by means of whichit may be oscillated from the dotted line off position to the full lineon position. I

According to my system I provide a servomotor I9 to actuate this lever.This is a fluidpressure servomotor comprising a cylinder 20 containingpiston 2i having an enlarged piston rod 22 projecting forwardly andprovided with a reduced end 23 pivotally connected with the lever H. Theopposite end of the cylinder 20 is pivotally connected at 23', to abracket 24 on the base block 25 mounted on the foundation I I or somepart of sure and the piston biased therefore rearwardly, 6Q

end of cylinder 2| to atmosphere.

thereby biasing control lever E1 of the power cut on and Mt ofi deviceto its rearward dotted line off position. The rear port 21 is indirectlyconnected to the source 23 through a fluid pressure relay valve 29 byway of a conduit 30 including the valve. The details of this valve arenot shown. Suffice it to say that it comprises a valve per se 3| whichwhen opened, admits fluid pressure to the rear of piston 2|, and which,when closed, cuts fluid pressure therefrom and exhausts the rear It isof a well known type. The valve 3! is actuated by diaphragm motor 32.

Motor 32 receives its fluid pressure under control of anelectro-pneumatic valve 33 comprising a valve per se, 34 and anelectro-magnet 35. When the electro-magnet 35-is energized, valve 34 isopened to admit fluid pressure by way of conduit 36 connecting it to thediaphragm motor 32 and when magnet 35 is de-energized, valve 34 closesofi the motor 32 from the source 23 and opens motor 32 to atmosphere,thereby closing valve 3|.

Circuit of electro-magnet 35 is controlled from a source of. electricpower 31 as applied through line switch 38 over conductors 39. Twocontrol means are provided. One 4|! is manual. It comprises a pluralityof pairs 4| of push buttons 42 arranged individually in series in acircuit 43 adapted to complete the connection of electromagnet 35 tosource 31 by way of conductor 39. The contacts of each pair are spreadso far apart that they cannot be spanned by one hand, but require to bereached one by each hand in order simultaneously to operate them.Moreover, they are placed at points requiring the removal of hands andlimbs of the operator beyond all danger regions of the dies and otherparts of the press to be avoided by the operator in the working stroke.Each pair 4| of contacts 42 is provided with a .by-pass 44 which isnormally opened but is adapted to be closed on special occasions byswitch 45, thus cutting out the pair and permitting the series circuit43, 39 to be completed without the particular pair or pairs cut out.This is to provide for cases of variation of the number of operatives,since each pair of contacts 4| provides for control by one operative,and it is required that a pair be provided for each operative to securesafety for all as well as for each.

The other of the means for completing the connection of the controlelectro-magnet 35 to the source of power 31 is a circuit 46 in parallelto the circuit 43 of the pairs of contacts 4| in series. Circuit 46 isnormally opened at spring contacts 41, but is adapted to be closed bythe projection of pin 46 between the adjacent ends of contacts 41. Pin48 is a pin of conducting material carried at the end of and insulatedfrom the body of a bell crank lever 49. This lever is actuated by a cammounted upon and angularly adjustable about the axis l6 of the maincrank shaft I15 of the press. Follower 5| on the opposite end of lever49 from the pin 48 rides on cam 50 and as the main crank shaft l5 of thepress revolves,

rides onto and off of cam 50 to open and close the circuit 46. Theangular adjustment of cam 50 asures that circuit 46 is opensubstantially at the extreme upper end of the upward stroke of thepress, remains open as follower 5| rides on cam 50 during substantiallythe entire down stroke of the press, and as the press moves into theextreme of its down stroke, the follower 5| rides off of cam 50 andcloses circuit 46 in parallel stroke.

with and independently of the push bottons 42 of the pairs 4|.

To operate the system one closes the switch 38 while the press is idleand the crank shaft substantially at the extreme "of its upward stroke,substantially 180 from the position shown. Each operative, as hefinishes his attention to the work on the machine, removes both handsfrom the work and assumes a'body position enabling him to reach bothbuttons 42 of the pair 4| assigned to him. By reason of the electricalcontrol, the buttons maybe arranged at any points on or near the machinemost convenient for the emcient movement of the particular operative towhom assigned. Each operative presses down the buttons assigned to him.When the last of the operatives has so pressed the buttons 42 assignedto him, and not until the last has so pressed them, can the circuit 39,43 of electromagnet 35 be completed. The instant it is completed, valve34 is opened, throwing fluid pressure from source 23 by conduit 36 upondiaphragm motor 32 and opening valve 3|, thereby throwing fluid pressureby conduit 33 upon the rear of the piston 2| to servo-motor 20.Immediately the piston 2| .is operated to the full line position shownthe press starts its downward stroke toward the dotted line positionshown.

At no time until the press reaches substan circuit 46 continues open atcontacts 41 until the dies or other parts l2, l3 are so close togetheras to preclude the entry of the hands or limbs of an operator between.When they have reached a position so close together, however, pin 48electrically connects contacts 41 and the press control circuit 46supplants the operatives control circuit 39, 43, whereupon theoperatives may freely release their hold on push buttons 42 and thepress will continue to the end of its downward stroke and to the end ofits upward stroke without further attention from the operator. Duringthis portion of the cycle, cam follower 5| has rolled ofi of the cam 50and remains oif until the press reaches the extreme of its upward Atthis instant it rolls again onto the cam 50, contacts 41are electricallyseparated, magnet 35 is de-energized, and valve 3| is opened to exhaustfluid pressure from motor 20 and throw the lever l1 from the full lineon position to the dotted line off position. Through the adjustment ofcam 50 in angular position and inusing duplex cam members which can beangularly adjusted relatively, as is well known to change the length ofoperation of the cam, the closure and opening of contacts 41 may beadjusted with respect to the end of the downward and the end of theupward stroke with great nicety.

' Thus are the ends and aims of my invention achieved.

It has been found that there is ample time during the upstroke foroperatives to move new work toward the press and to feed it in withoutundue loss of time between press strokes. The rate of operation ofpresses with this system installed is quite as high as that of pressesin which it has not been installed, and workmen are free angular extent,either by changing cams or by to move work toward the press after thedanger 7,5

period of approach to the approaching parts of the machine has passed.

If at any time electric power goes oiT, by reason of the normal bias ofpiston 2| towards the off position by the connection of its front end.

to the source of fiuid pressure 28, the press is stopped immediately. Itcan only be started again by manual operation. Such connection to fiuidpressure also eliminates necessity for powerful springs and attendantwear and possible breakage, or the need for double action fluid pressurecontrol.

The generic spirit of the invention should govern the scope of itsclaims independently of the circumstantial terminology used therein, inview of the substantial contribution over the prior art and theunavoidable evolution of modification and improvement.

What I claim is:

l. A safety system for power presses comprising a fluid actuated servomotor biased to inactive position, a differential pressure arrangementto actuate said motor, electrical means arranged to initiate saidpressure means, a plurality of spaced switches in series circuit,arranged to energize said means, and a lock-in circuit arranged tomaintain said electrical means energized during the extreme approachmotion of the dies and during the retrograde motion of the dies only andindependently of said manual means.

2. A safety system for power presses comprising a fluid actuated servomotor biased to inactive position, .a diiierential pressure arrangementto actuate said motoryelectrical means arranged to initiate saidpressure means, a plurality of spaced switches in series circuit,arranged to energize said means, and a lock-in circuit arranged tomaintain said electrical means energized during the extreme approachmotion of the dies and during the retrograde motion of the dies only,said lock-in circuit only becoming operative due to the continuedsimultaneous actuation of said series switches throughout the approachdie movement up to their extreme approach motion.

3. A safety system for presses comprising a pneumatically operated powercontrol device, electrical means to control said device and parallelcontrol circuits for said means, one of said circuits including aplurality of spaced switches in series circuit arranged to initiate saidmeans upon simultaneous actuation thereof and to continue theenergization thereof during the major approach motion of said press uponsaid continued actuation thereof, said other circuit comprising a mastercircuit to continue the press cycle of operation independently of saidfirst named circuit during the extreme approach and retrograde motionsonly of said press.

4. In combination, a machine including ele- I ments for operation on anobject, means controlling operation thereof, a fluid source, a fluidresponsive motor connected to the control means and having large andsmall pressure faces operating the control means and, respectively,actuating and stopping the machine, a fluid responsive valve, the smallpressure face being constantly connected to the fluid source and thelarge face being connected to the source through said valve, a conduitincluding an electro-responsive valve connecting the fluid source tomeans controlling the first valve, a source of electromotive force, aplurality of pairs of switches in series circuit relation between theelectro-responsive valve and the electromotive source, each pair beinginaccessible to an operator of another and the .switches of each pairrequiring operation by the separate han$ of 5 its operator, a circuitincluding a switch shunting the pairs, and means controlled by themachine for closing the shunt switch to operate the machine during afinal portion of the .approach, and during all of the separating,movement of the machine elements.

5. In combination, a machine including elements for operation on anobject, means controlling operation thereof, energy source means, amotor connected to the control means and in- 15 eluding high and lowenergy receiving portions operating the control means and, respectively,actuating and stopping the machine, a valve or the like, the low energyportion being constantly connected to the energy source means and thehigh energy portion being connected to the source through said valve,means including a valve or the like connecting the energy source meansto means controlling the first valve, a plurality of pairs of switchesor the like in series relation between said second valve and the energysource means, each pair being inaccessible to an operator of another andthe switches of each pair requiring operation by the separate hands ofits operator, means including a switch or the like shunting the pairs,and means controlled by the machine for closing the shunt switch tooperate the machine during a final portion of the approach, and duringall of the separating, movement of the machine elements.

6. In combination, in a machine including members relativelyreciprocable by a substantial distance for working on objects requiringplacement, and removal from, between the members by a plurality ofoperators stationed at different positions, actuating means for theelements, control means for the actuating means biased towardinoperative position, and governing means for the biasing meansincluding a plurality of pairs of interdependent handles correspondingto the number of operators and each spaced from the machine beyond thereach of an operator stationed to handle the object, each pair ofhandles being disposed at a position normally inaccessible to anoperator at another and the handles of each pair being normally spacedto require manipulation by the respective hands of its operator, andmeans controlled by the machine for rendering the handles ineffectiveand controlling the actuating means to 65 operate the machineindependently of the handles during a final portion of the approach, andduring .a portion of the separating movement of the said machine membersrelative to the object.

7. A safety system for presses comprising a power cut on and cut offdevice of the press, and parallel control devices for said power cut onand cut off device, one manual and the other automatic, the latter beingunder control of the press in its upward stroke substantially .at theextreme upper end of said stroke only, and on the downward stroke of thepress being under control thereof during substantially the entiredownward stroke, said manual means requiring a plurality of pairs ofhands for operation.

oARoLus L. EKSERGIAN.

